The present invention relates to a head maintenance mechanism for a serial type ink jet printer in which a carriage mounting thereon a print head is reciprocated in a widthwise direction of printing. More specifically, the invention relates to a head maintenance mechanism in which a single rotary drive source is used to drive a head cap, wiper and an ink suction pump.
With a serial type ink jet printer, a head maintenance mechanism is arranged in a position outside a region of printing performed by a print head, and wiping of dirt on a nozzle surface of the print head, capping intended for prevention of plugging of a nozzle orifice, and an operation of sucking ink in an increased viscosity from the nozzle orifice are performed by the head maintenance mechanism. To meet the needs of making a head maintenance mechanism for an ink jet printer small-sized, compact and inexpensive, related art head maintenance mechanisms are constituted by a configuration in which a single rotary drive source, such as stepping motors or the like, is used to cause movement of a wiper for wiping a nozzle surface, a capping action of a head cap for capping the nozzle surface, and an operation of sucking ink from a nozzle orifice as capped.
For example, Japanese Patent Publication No. 2000-141673A discloses a head maintenance mechanism of such configuration. With the head maintenance mechanism disclosed in this publication, rotation of a single motor in one direction causes a head cap and a wiper to be driven through a slide type rack and a cam mechanism, and reverse rotation of the motor causes a diaphragm suction pump to be driven through a cylindrical cam.
However, a head maintenance mechanism of a type in which rotation of a single motor in one direction causes a head cap and a wiper to be driven, and reverse rotation of the motor causes a suction pump to be driven, involves the following problems.
First, a cylindrical cam is generally used to convert rotary movements of a motor into reciprocal movements. Since such a cylindrical cam is continuously rotationally driven in one direction, there is a need of providing a position detector for detecting a reference or initial position of the cylindrical cam in order to control respective motions of the cylindrical cam.
Also, there is a need of separately providing a power transmitting mechanism for driving of a head cap and a wiper and a power transmitting mechanism for driving of an ink suction pump, which is disadvantageous in making a head maintenance mechanism small-sized and compact.
Further, a pump, for example, a tube pump needed to rotate forward and rearward cannot be adopted as an ink suction pump. More specifically, in the case where a tube pump is used, a roller rotates flattening an ink tube to perform an ink sucking action when a pump gear being a drive force input element of the pump is rotated forward, and the roller is put in a release state, in which the ink tube is not flattened, when the pump gear is rotated rearward. Since the release state is necessary after the ink sucking action, a tube pump cannot be used in the case of rotary driving in one direction.
Also, a head maintenance mechanism for an ink jet printer involves as an ink sucking configuration from a head cap with an ink sucking action, the case where ink is sucked from a nozzle orifice and the case where ink accumulated in the head cap is sucked (idle suction) in a state in which the head cap made in capping is put in an atmospheric opening state. In order to realize both of these ink sucking configurations, it is necessary to provide a mechanism for opening and closing a vent valve mounted on a head cap after there is established a state in which the head cap caps the nozzle surface. When such mechanism can be made compact, it is advantageous in making a head maintenance mechanism small-sized, compact or thin.